John Sayles makes long movies that are dull in places, but eventually he gets somewhere, and he does with "Honeydripper," his rumination about the birth of rock 'n' roll in the Deep South. The scene is Alabama in 1950, in a club called the Honeydripper Lounge, where the owner decides to bring in some new sounds to attract a younger clientele.

Even more than the music in this musically rich picture, the great pleasure of "Honeydripper" is in watching Danny Glover as Tyrone Purvis, the club owner. Playing a man trying to stay afloat in the face of competition, hard times and a white sheriff (Stacy Keach), Glover changes his walk, stiffens his posture and even tightens his facial expressions. I have seen the man he's playing, or men like him, but not for a long time. What Glover is doing is channeling a certain type he once knew, a kind of man who was a certain age when Glover was very young. Watching Glover here is like watching memory made flesh, or some psychic excavation. It's going back in time.

Yet it's subtle - the subtlety is the beauty of it. You won't notice if you don't pay attention, but if you do, you'll see it all in Glover's face and in the way he carries himself: a dignity that's innate but also earned, the wariness and dread that keep his back tense and straight, and a painful past that manifests as gentleness toward the weak. When you watch him, you'll have no doubt that this is a black man who has spent his whole life in the segregated South but has somehow managed not to break or even bend.

He's a character we'd like to spend some time with, and we do. Sayles likes to let his movies breathe. Sometimes he lets them breathe until they die, but he can afford to luxuriate in the atmosphere of "Honeydripper" because his story is simple and dramatic: This is Purvis' big weekend. If he makes enough money, he can pay off the mob, pay off the sheriff and keep his club. If he doesn't, he'll lose everything and probably get his legs broken - at least.

The Alabama town is lonely in its smallness and poverty and with the whistle of the train going by, always heading somewhere else. But the music is the evidence of things unseen. The town's longing and its life of the spirit come out in the blues and in the exuberance of early rock 'n' roll. The blues may be sad, and rock 'n' roll might be happy, but they're both about resiliency - about facing things and coming back, if only with a song. And so it should come as no surprise that after a slow but considered opening, "Honeydripper" picks up.

Glover, who's wonderful, isn't alone out there. Yaya DaCosta is touching as his delicate daughter, too lovely for this place, and Keach as the sheriff is fascinating to watch. His face is cold but not impassive, and it's possible to read in his eyes every gradation of envy, admiration, fear, resentment and sadistic amusement that he experiences as he looks at Purvis.

Meanwhile, real-life guitarist and singer Gary Clark Jr. keeps the club jumping as Sonny, an early rock 'n' roller who stumbles into town with one of the first-ever electric guitars. Among the many smart things Sayles did in "Honeydripper" is record the music live on the set so that Clark wouldn't have to mouth the words to a canned track. The energy onscreen makes its way into the audience.